Clinical characteristics and predictors of mortality in patients with Enterobacter aerogenes bacteremia

Enterobacter aerogenes is increasingly encountered in nosocomial infections. This study aimed to clarify the clinical characteristics and to identify the predictors of mortality in patients with E. aerogenes bacteremia.

From March 2001 to April 2007, all patients with positive blood cultures for E. aerogenes at Taipei Veterans General Hospital, Taipei, Taiwan, were enrolled in this retrospective study. The medical records were reviewed for clinical and laboratory data.

Eighty eight patients were included, 9 (10.2%) of whom died of E. aerogenes bacteremia. Most of the patients had comorbidities. Seventy nine patients (89.8%) had nosocomial infections, and 43 patients (48.9%) had polymicrobial infections. Eighty four patients (95.5%) presented with fever. Empirical antimicrobial therapy was administered for 80 patients (90.9%), but was appropriate for only 55 patients (62.5%). Of the 9 patients who died, 8 had polymicrobial infection, 5 of whom had nosocomial pneumonia, and 6 did not receive appropriate antimicrobial therapy. Multivariate analysis indicated that high Acute Physiology and Chronic Health Evaluation (APACHE) II score (>16) [odds ratio (OR), 16.569; 95% confidence interval (CI), 1.24-221.24; p = 0.034] and strains not susceptible to extended-spectrum cephalosporins (OR, 9.21; 95% CI, 1.02-83.04; p = 0.048) were independent risk factors for mortality.

The severity of E. aerogenes bacteremia, reflected by high APACHE II score and isolation of strains with no susceptibility to extended-spectrum cephalosporins, were independent risk factors for mortality. Patients with severe illness and isolates resistant to extended-spectrum cephalosporins should be treated with more potent antimicrobial agents.